Anyhow, yesterday, out of the blue, she started to behave funny. I thought at first that it was slipping but as the problem got worse during the day I realized that what was happening was that it kept downshifting. If I was in 4th, it went to 3rd. If I was in 3rd, it went to 2nd. But it would bounce between the two gears repeatedly, especially with a light throttle.

If I was on the highway and slowing for a toll booth it would jump between 4th and third so dramatically that I had to shift into neutral.

A somewhat heavy foot on the throttle makes it pick a gear, especially if I am opening the throttle fast enough to "bog" the engine.

The overall behavior, especially with regards to throttle position vs RPM leads me to suspect that it is somehow related to a vacuum signal, but I really don't know squat about Isuzu systems.

Has anyone come across this before?

I know even less than squat about izusu's (see, I can't even spell it) but if it were a jeep, I'd say you need to do a throttle valve linkage adjustment and replace the fluid. If it's been changed fairly recently but the fluid smells burned, look into getting a tranny cooler.

There use to be a Isuzu list ( not the ITOG one) . I think it was hosted by vmags. I couldn't find it by doing a google search but it's a great list if you find it. My kid has a 92trooper and that list was great!
I'll keep looking , it had a great archive of stuff, if you find it pass it on back,

thanks

bennett